The present invention relates to the removal of mercaptans or thioalcohols, from gas mixtures, particularly gas mixtures containing hydrocarbons such as, for example, natural gas.
The removal of sulphur compounds from gas streams has been of considerable importance in the past and is of greater importance today due to environmental concerns. Gas effluent from the combustion of organic materials, such as coal, almost always contains sulfur compounds and sulfur removal processes have concentrated on removing these sulfur compounds since it has been determined that some of them pose significant health hazards. With increasing emphasis on the elimination of sulfur discharge to the atmosphere and utilization of natural gas streams that were heretofore unusable due to their sulfur content, attention is turning to the removal of sulfur compounds from gas streams.
Numerous natural gas wells produce what is called in the industry "sour gas". Sour gas is natural gas that contains sulfur compounds, especially hydrogen sulfide, in concentrations that make its use unacceptable as for example in home heating uses, refinery feed gases, etc. Considerable effort has been expended in finding effective and cost efficient processes to remove these objectionable sulfur compounds from natural gas. There has been extensive work done in developing process for the removal of hydrogen sulfide from gas treatments such as natural gas streams. Indeed, the patent literature is replete with processes for the removal of H.sub.2 S from natural gas streams as well as other gas streams containing H.sub.2 S.
There are some natural gas streams which are "sour", not because they contain hydrogen sulfide but because they contain objectionable levels of mercaptans. Insofar as the end use of these natural gas streams are concerned, the mercaptans are virtually as objectionable as hydrogen sulfide, mainly because of odor, albeit that for the most part they are not as toxic as hydrogen sulfide.
Examples of patented processes for the removal of mercaptans from gas streams include U.S. Pat. Nos. 4,412,913; 4,462,968; 4,540,552; 4,460,395. U.S. Pat. No. 4,515,759 discloses a process for removing hydrogen sulfide from gas mixtures by treating the gas mixture with an aqueous medium containing a water soluble nitrite such as sodium nitrite. However, the patent does not disclose the removal of mercaptans or other similar organic sulfide compounds from gas streams.